With the precision of a surgeon donning scrubs, Sharon Peregoy shrugs on a burka-like white shroud. Though she’s been up for hours, the sun is just rising behind her in suburban Maryland. She’s already flashed her government ID to a guard, parked her car, and passed the sign at the entrance of the nondescript building that reads keep it quiet. Now she adjusts a camouflage veil over her face and slips her hand into the long neck of a puppet. It’s a slender approximation of a whooping crane, with a beak she can operate like a pair of chunky chopsticks. Exit Peregoy—lanky, blonde, and decidedly human. Enter “the Costume.”

Unlatching a gate, the Costume slips into a small walk-in pen, an MP3 player purring gently from its pocket. A cinnamon-colored whooping crane chick snaps to attention, tottering over with an excited preep! As the crane approaches, the puppet comes to life, waggling its head and dipping its beak into a plastic dish of brownish pellets. When the Costume stirs the food, the chick moves dishward. Soon it’s swallowing crumbs.

The Costume and the chick are players in an intense experiment—part science, part performance art— based at the United States Geological Survey’s Patuxent Wildlife Research Center, in Laurel, Maryland, and at four other private facilities scattered around the country. Now just three days old, this chick will one day stand five feet tall with an eight-foot wingspan. Its trumpeting call will carry for miles. But who will answer that call is in question: Whooping cranes are a critically endangered species.

Aggressive, solitary, long-lived, monogamous, slow to reproduce, the birds are picky about what they eat. They also live and breed in marshes and wetlands—some of the most imperiled ecosystems in the country. These peculiarities present a monumental challenge for the scientists who have been trying to save the species from extinction for 40 years now. It’s an undertaking so difficult that biologists liken it to putting a man on the moon. “That [their] existence depends on our everyday work is something that’s in the back of our minds all the time,” Peregoy says. That she’s in a costume every day, impersonating a mother crane, shows the lengths she’s willing to go.

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On July 6, 1967, a whooping crane chick hatched at the San Antonio Zoo. The zoo’s director, Fred Stark, was delighted: The chick’s wild-hatched parents, Rosie and Crip, were only the second pair of whoopers ever to reproduce in captivity. But two days later, the chick was dead, inadvertently smothered by its clumsy first-time mom. When the second viable egg hatched a couple of days later, Stark plucked the still damp and exhausted chick from its parents’ nest and slipped it into a cardboard box under a heat lamp in his living room.

The chick—Stark named her Tex—warranted special attention since the cranes were almost extinct. A 1942 survey had found only 22 wild whooping cranes left in all of North America. Then, a 1948 storm killed all six of Louisiana’s, bringing the population to a devastating new low. It wasn’t until the late 1960s that American biologists launched an all-out effort to breed the bird in captivity.

When Tex was just a few weeks old, Stark turned her over to the U.S. Fish and Wildlife Service, where she grew up happily. She happened to have rare genes that could add much-needed diversity to the population’s shrinking gene pool, so once she reached adulthood, scientists were eager to breed her. But there was a problem: They couldn’t get Tex in the mood. So in 1976, an ornithologist named George Archibald hatched a plan to change her mind.

Archibald and fellow grad student Ron Sauey had recently co-founded the International Crane Foundation (ICF), in Baraboo, Wisconsin. The young scientists hoped to create a gene bank by breeding all the world’s 15 crane species—a goal that seemed critical given most cranes’ vulnerable status. Tex was loaned to the project because, despite her valuable genes, she’d turned out to be something of a lemon from a breeding standpoint.

Archibald believed Tex’s problems could be ascribed to an animal behavior first studied by the Austrian scientist Konrad Lorenz in the 1960s. When large birds such as ducks and geese and cranes hatch, they immediately form an irreversible attachment to the first big moving object they clap eyes on (which, if nature works as intended, will be Mom or Dad). The babies will follow that object, mimic it, learn from it, and, as adults, desire to mate only with others of its kind.

Lorenz called this innate behavior “imprinting,” and his experiments demonstrated what kind of loyalty this love at first sight could produce. For instance, when he showed his legs to a newly hatched clutch of geese and got them to imprint on his Wellington boots, the babies tumbled behind him whenever he wore them. He got another clutch to imprint on a box mounted on a model train; these goslings galloped behind the box as it circled the track.

Tex, it was clear, had imprinted on her foster father, Fred Stark. In saving Tex’s life, Stark had sealed her fate: Tex’s lifelong sexual preference would be for men. If Tex were left to her own devices, she would never lay eggs, and her genes would be lost.

Archibald put Tex in a grassy pen near his office, where he slept each night on a cot. For seven long weeks, man wooed crane. Archibald whooped and flapped and leaped about in a whooping crane’s ritual mating dance, his curly brown hair flying about in a most un-cranelike manner. Sure enough, Tex fell hard. Soon the two were whooping in unison. The courtship behavior stimulated Tex’s reproductive hormones, and she began ovulating. Then Archibald and his team artificially inseminated Tex with semen from a captive male whooper. She laid many eggs, but they were all blank.

Archibald and Tex renewed their courtship over subsequent springs. (Archibald, devoted but not insane, had hoped Tex might agree to court other men; she did not.) Then, in 1982, she laid a single viable egg. Archibald was elated. The mottled greenish egg, too precious to entrust to Tex’s inexperienced parenting, was incubated and closely monitored. In June, a live male chick hatched. They named him Gee Whiz.

The joyous news spread quickly through the media; Archibald and the cranes became a sensation. In July 1982, he was invited to appear on the The Tonight Show with Johnny Carson. Archibald was preparing to take the stage in Los Angeles when he got a terrible phone call. On television he shared the news: Raccoons had gotten into Tex’s pen. She was dead.

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In the post-Tex era, biologists redoubled their efforts to crack the whooping crane code. Their goal: whooping cranes that could breed and live on their own. At ICF and at Patuxent, crane specialists began devising a protocol to which all whooper breeding facilities now adhere and in which, over the course of a season, more than a hundred techs, interns, and volunteers take part. It’s an elaborate ruse to bypass human imprinting, and it begins before the chick is even born. “It’s not the easiest thing to explain at a cocktail party,” Peregoy says.

Today, 50 or so whooping crane eggs are produced every year by captive whoopers, whose population is now some 150-strong. These birds are fostered by captive sandhill cranes, the whooper’s easygoing cousins. But chicks fostered by sandhills can’t be allowed to imprint on their foster parents because then they’ll reject whooping cranes when they’re ready to mate.

So, before the chicks hatch, the researchers intervene. When the whooping crane eggs are near term, handlers transfer them from the foster sandhill nests to a climate-controlled hatchery. There, researchers monitor the eggs carefully, waiting for them to peep and roll around.

Eventually, the chick punches a perforated line around the top of the shell, alternately resting and stabbing until it breaks free. Because birds tend to be naturally aggressive toward nest mates, each chick must hatch in isolation. But through careful planning, the scientists ensure that once it hatches, the first thing the newborn sees is an adult whooping crane—through a sheet of plexiglass. Setting eyes upon this “mother,” the chick galumphs unsteadily toward her. Then—whap!—it smacks into the plexi and tumbles over, forever and ever a whooping crane. From here, the biologists move the imprinted chick to its own pen, where it’s welcomed by a taxidermied brooding crane outfitted with a warming light under its outstretched wing. This is where the Costume comes in. So that the chick never sees a human figure, the Costume drops in every few hours to make sure the tyke is eating and drinking. At intervals over the weeks, another shrouded figure appears. “For everything that’s scary and bad, like the medical checks, we change to a gray costume with no puppet,” says Kim Boardman, crane handler at ICF. “We never want the Costume to be associated with bad experiences.”

Over the next few weeks, as the chicks shed their golden fluff and grow into their cinnamon plumage, the Costume walks them outside and shows them how to forage for worms, tadpoles, and insects. Swimming and standing-in-the-marsh lessons begin. An important exercise regimen of dashing through meadows balances growth with weight gain. Soon enough, chicks are introduced to one another—tense moments for all concerned—and gradually socialized so that they can be tended in a flock. With luck, these hatchlings will grow to become ivory-feathered adults capable of accomplishing the next feat on a crane’s agenda: migration.

Each year, the nearly 400 whooping cranes—both wild hatched and Costume reared—living in North America’s marshes spend their summers breeding in the prairie potholes and taiga of Canada’s Northwest Territories. Then, in the fall, they migrate nearly 2,500 miles to the bayous of the Texas Gulf Coast. Covering this route only once, in the company of its parents, a young crane can make the journey on its own for the rest of its life. But how could the Costume possibly teach its chicks this skill?

In 1992, an ultralight-aircraft-obsessed Canadian pilot named William Lishman witnessed a flock of imprinted geese following a boat. He’d always dreamed of flying with birds; now he saw how it could be done. Lishman approached the whooping crane researchers with an outrageous proposal: He would teach whooper colts to migrate behind an ultralight— basically a winged tricycle with a three-blade propeller—piloted by the Costume. In 1993, Lishman, along with Joe Duff, lead pilot for Operation Migration, tested his proposition with imprinted Canada geese (dramatized in the film Fly Away Home). It worked. Holding their collective breath, the crane biologists gave him the go-ahead to try with their birds.

To train the colts, Lishman first drove his ultralight in circles on the ground. Dribbling treats behind him, he got the attention of the flock. Next, they made short, then longer flights. In 2001, the first flock of seven Costume-reared chicks made their way south behind the aircraft. A ground crew with portable pens, food, RVs, and other necessities followed the squadron on the ground. Overnighting and sitting out bad weather at preselected stopover sites, just as wild birds would, the cranes arrived six weeks later in central Florida. Last year, Operation Migration celebrated its 13th successful annual costumed migration.

Today, the Whooping Crane Eastern Partnership— which has eight partners, including both Patuxent and ICF with about 50 full-time crane staff combined; federal and state agencies; funding partners; and three nonprofits—is a model for other restoration efforts.

“It’s humbling to get to play even such a small part in this effort,” Patuxent’s Peregoy says. She knows that, despite the intense dedication of the researchers involved, there are still challenges ahead. After all, nature had 40 million years to fine-tune whooping crane biology. Technology and good intentions can only play catch-up.

This story originally appeared in an issue of mental_floss magazine. Subscribe here.